Who is Tim Cook?

Since Monday’s announcement that Steve Jobs would take his third medical leave of absence from Apple AAPL, much attention has been focused on his #2, COO Tim Cook.

“I have asked Tim Cook to be responsible for all of Apple’s day to day operations,” Jobs said in his letter to the Apple team, which was also released to the media. “I have great confidence that Tim and the rest of the executive management team will do a terrific job executing the exciting plans we have in place for 2011.”

In November 2008, on the verge of Jobs’s second medical leave, Fortune‘s Adam Lashinsky wrote a definitive profile of Cook, who functions at Apple as the calm to Jobs’s storm.

“Let’s start with some uncomfortable truths,” Lashinsky begins. “We wouldn’t be publishing an article about the under-the-radar guy who’s most likely to succeed Steve Jobs as chief executive of Apple if Jobs himself hadn’t shown up at a company event in San Francisco in June looking frightfully skinny and pale.”

With Jobs’s latest leave, a different version of those same uncomfortable truths make understanding the man who will be running Apple — indefinitely — even more important for shareholders and investors than ever before.